Leather-making process



"UNITED srArss smear OFFICE.

IGAN; SAID wILsoN AssrGNon on His ENTIRE RIGHT TO VICTOR, N, BRANT, or

BRISTOL, INDIAN A.

LEATHER-MAKING PROCESS.

No Drawing.

To all whom it may concern Be it known that we, PAUL BRANT, of the city of Bristol, county of Elkhart, and State of Indiana, and HERMAN T. WILsoN, of Petoskey, county of Emmet, and State of Michigan, have invented certain new and useful Improvements in Leather-Malnng Processes, of which the" following is a speclfication.

This invention relates to a new, novel and efficient method of filling, weighting and water-proofing leather, by impregnating the same with compounds which are not only quite insoluble in water, but which, belng non-adulterants, add real value as well as weight to the finished product, and compos1- tion of matter therefor.

In the usual practice in the production of heavy leathers, the hides (after bemg tanned in a succession of tanning liquors) are bleached, oiled, and. then filled with various materials well known in the art, in an attempt to produce desirable solidity and weight in the leather, but the several fillmg or loading materials in general use in the manufacture. and tanning of leather are soluble in water, and may be soaked out of the leather in every day use and lost, and are for various other reasons often objectionable in the finished marketable leather.

Some of the principal objects of our invention are to provide a new, novel and efiicient process for the fixation of soluble tannins in leather; to convert uncombined tannins into precipitated leather; to impregnate leather with amorphous leather; to produce increased weight and waterproofness; toprovide a new and useful method and process for weightlng and water-proofing leather; and to provide new and useful compositions of matter for accomplishing the above objects.

The above and other features of novelty, advantages and capabilities of our invention become apparent from the accompanying description, in which we have described the preferred forms of our invention, but it is to be understood that the particular forms described are illustrative only, and do not define the limits of our invention.

With our invention, the leather is impregnated with compounds of glue, gelatin, or other albuminous or proteid bodies,

Specification of Letters Patent.

Patented May 17, 1921.

A Application filed July 31, 1918. Serial N0. 247,507.

which have the power of combining with tannins and the compounds formed by these and the soluble tannins in the leather are so fixed within the leather fabric as to become insoluble under ordinaryconditions. It is also practical when weighting and water-proofness alone are desired, to im- "IPAUL BRANT, OF BRISTOL, INDIANA, AND HERMAN T. WILSON, OF PETOSKEY, MIGH- pre nate the leather with a mixture of glue an any suitable tannin, such as quebracho, mimosa, sumac, etc. Either of these mixtures is fixed with acid materials within the leather fiber as an insoluble loading or filling agent. This fixation process produces a material which is not unlike leather itself and may be termed precipitated leather.

The tanned or partly tanned leather, when taken from the tan-liquor vats and partly dried, has a layer consisting lar ely of tannins and reds upon its surface, and also contains distributed throughout its body a considerable amount of tannins which are uncombined with the hide substance, and act only as a weighting material. present process, we seek to convert the free tannins into a more usefulprodu'ct, viz., precipitated leather, by reacting thereon with glue or equivalent material and precipitating same, or we can impregnate the tannin soaked leather with a mixture of glue and tannins and precipitate same. This last procedure has little if any fixing powers upon the uncombined tannins before In the mentioned, and is a weighting and waterproofing process only. By the term uncombined tannin is meant that which is in vegetable tanned leather in excess of that fixed with the hide substance of. the hide fiber.

In applying the process of either part of may be sufficient to render the leather fit for treatment by the following steps of our process now to be described.

The partially dried or wrun leather is put into a stufiing drum, 6. 9., sue a drum as is commonly used in tanneries, and therein treated with an alkaline solution of glue or other kindred materials, as previously mentioned, or mixtures of these or with an alkaline solution of glue and tannin. It is also of importance that if the leather has not been previously oiled that the alkaline glue or the alkaline glue and tannin solution should contain a certain amount of mineral or sulable mineral oil or mixture of oils. Or the following solution is an exampleof one to be used per one hundred pounds of leather to be treated,two to ten pounds of glue, two to twenty pounds of tannin liquor or tannin extract, two ounces to three pounds of caustic soda or an equivalent amount of any suitable alkali, and one-half quart to two gallons of a suitable mineral oil or mixture of oils, all of the above in from three-quarters to two and one-half gallons of water.

As a specific example of a test run, which proved satisfactory, the following may be cited:

Glue 40 pounds, Water 6 gallons. Tannin extract 16 pounds, Caustic soda 6% pounds, Mineral oil 11 quarts,

Sulfonated oil This was suflicient for. one thousand pounds of leather.

It is, of course, understood that these proportions may vary with differentclasses of leather, and according to the gain desired.

After the drum containing the leather has been set in motion, the glue solution or the glue and tannin solution should be added through the hollow gudgeon at a temperature ordinarily used in drufn filling, say 150 4 quarts.

i to 180 F., and the rotation continued from twenty minutes to one hour, during which time the leather will absorb substantially the entire quantity of the impregnating solution. It is generally, although not always,

necessary to dry the leather treated as above for from twelve to twenty-four hours before following with the acid treatment to be described.

After returning the semi-dried leather to i the drum, whether the glue solution or the glue and tannin solution has been used, the drying treatment is followed by an acid treatment consisting of one to three pounds of mineral acid, 6. 9., sulfuric acid, or an equivalent amount of a strong organic acid, e. 9., acetic or lactic acid, or an equivalent amount of any proper acid salt, e. 9., sodium bisulfate, diluted with one to three gallons of water. It is the intention that the terms acid solution, acid wash, etc., used in the claims shall include both a solution of an acid and a solution of an acid salt. This treatment is also preferably performed in a revolving drum and may take place in the same drum in which the previous operation has been effected. This acid solution penetrating the leather neutralizes the alkalinity of the impregnating solution and precipitates within the leather fabric compounds of glue and tannin, which compounds constitute a variety of artificial leather, or as above styled, precipitated leather. Being of substantially the same chemical nature as real leather, these precipitated bodies do not constitute an adulteration of leather, but rather an addition thereto, produced in situ within the body of the original leather.

It is also advantageous at times to add from one toeight ounces of aluminum sulfate or magnesium sulfate to the acid fixing solution. This has considerable effect upon the color of the finished leather through afthen follow with the alkaline glue treatment or the alkaline glue and tannin treatment, and subsequent fixation by acids or acid salts or both. Also, if desired, it is possible to employ, when weight and water-proofing alone are desired, an alkaline tannin solution followed by an alkaline glue solution and then by an acid wash, or these treatments may be effected in difierent ordersif desired.

The leather is now hung to partially-dry after any approved method, afterwhich it may be drummed with glucose, oils, etc., and finished in the usual manner.

Leather produced by the herein described treatment by glue or glue andtannin possesses solid and strong texture, a good color, and as all minute holes in the leatherhave been plugged up by the precipitated leather, a superior degree of water-proofness as compared with leather not so treated. It is quite impossible to narrowly define any given quantities ofglue or glue and tannin, which should be used in our process on account of the extremely wide range in the percentage of uncombined tannins of widely differing tannages. As this "percentage is, however, generally known or readily ascertained by the tanner as applying to his individual tannage, the matter becomes simple, as it is only necessary to add approximately such a quantity of glue as will combine with the uncombined tannins known to be present, or to add a quantity of glue and tannin, which after fixation will leave the uncombined tannins undisturbed. This combining ratio to form the precipitated leather is for all practical purposes one to one.

While we have described various modes of applying the glue or glue and tannin solution, we prefer to treat the semi-dry leather containing free tannin with an alkaline solution of glue containing oil or an alkaline glue and tannin solution containing oil and after again partially drying to treat with an acid liquor containing aluminum or magnesium sulfates in such quantities as to obtain the color sought. In this mode of operation, the alkaline liquor exerts a solvent action on the free tannins and even on the relatively insoluble tcnnins and reds, which materials are thereby carried into the interior of the leather and subsequently react with the glue upon application of the acid liquor.

In practising this process, we would also call attention to the fact that the long time ordinarily consumed in vat tannage may be materially shortened. As a rule, the hides become tanned through before receiving the last and strongest liquors in the yard, these liquors later serving largely the capacity of filling agents. With our process, it is possible to take the hides from that layer in which they are first completely struck through, subject them to the glue or glue and tannin process, and thereby materially lessen the yard time and cost.

In the above description, we have referred mainly to glue but call attention to the fact that gelatin or other albuminous or nitrogenous bodies (proteid matter generally) capable of combining with tannin may be used. The coagulation and fixation of the compounds may be accomplished by other agents than acids or acid salts, as for example aluminum sulfate, magnesium sulfate, sodium chlorid, etc., which react with considerable power in this capacity.

Having now described our invention, we claim:

1. That part of the process of making leather which comprises subjecting the partly prepared leather containing tannin to the action of dissolved gluey matter and tannin in the presence of an alkaline material, and thereafter to an acid solution.

2. That part of the process of making leather which comprises treating partly prepared leather containing tannin with an alkaline glue solution and then treating it with a solution containing free acid capable of combining with previously added albuminous matter to cause fixation thereof.

3. The process of fixing glue and uncombined tannin in leather, which comprises treating the same with an alkaline glue solution, and subsequently with a solution containing free acid capable of reacting with the alkaline-glue solution contained in the leather to neutralize the same and precipitate the albuminous matter in the leather.

4. That part of the process of making leather which comprises the following steps: subjecting leather to an alkaline-glue solution, then to an alkaline-tannin solution, then to an acid wash, whereby an insoluble material is formed within the leather.

5. Those steps in the process of mak ing leather which comprise impregnating leather containing tannin with suitable alkaline albuminous material, and fixing the same in the leather by treatment with a solution containing free acid capable of neu-' tralizing the alkali and fixing the albuminous substance in the leather.

6. In a leather making process, the following steps: impregnating leather containing tannin with an alkaline albuminous solution, whereby to form an albuminous tannin compound with the uncombined tannins in the leather, and fixing said compound by thedaddition of a solution containing free ac1 7. Those steps in the process of mak ing leather which comprise impregnating leather, containing uncombined tannin, with suitable alkaline albuminous materials and then treating the leather in a solution containing free acid.

8. Those steps in the process of making leather which comprise impregnating the process prepared leather with an alkaline solution of gluey matter and tannin and then treating the same with a solution containing a free acid, thereby producing in the leather a relatively insoluble filling and weighting compound.

9. That part of the process of making leather which comprises treating the leather which has been partly or wholly tanned,

with an alkaline glue solution, and then treating it with a solution containing an acid salt capable of combining with previously added leather contents to cause fixation or precipitation thereof.

10. Those steps in the process of making leather which comprise impregnating leather, containing uncombined tannin, with suitable alkaline albuminous materials and then treating the leather in a solution having an acid reaction.

In witness whereof, we hereunto subscribe our names to this specification.

- PAUL BRANT.

HERMAN T. WILSON. 

